THE FRESH-WATER MUSSEL 



125 



around the intestine, and thin-walled right and left auricles which lead 

 from the sides of the pericardial cavity. Blood leaves the heart by 



/eft aur/c/e. 



suprabranch/a/ 



pcr/corcf/a/ coi^/'ty. 

 r/ght aunc/& 



,^nep/7r/Q'/'tfm 



mont/& 

 ve/n 



tL/ph/os>o/e.- - 



efferent 

 /?ranchia/ 

 ueeefe/-' 



afferent /?ronc/?/a/ 



left ontferfor mantle 



Foot 

 (uti//zation cf foocf 

 ape/ aiugeniproa/uc 

 t/on of excret/ons) 



_ _ - -Mantle, 



(external respiration 

 ana excretion) 



left mantle vein 



3tomacn-/nt€3tinei 

 (absorption) 



C//b 



(external respiration 

 ancf excretion) 



Rectum 

 (absorption) 



Nephridium 

 (excretion) 



Fig. 59. — The circulatory system of Anodonta. Above, diagrammatic cross 

 section of the massel, showing the heart and principal blood vessels. Below, 

 diagram showing the course of circulation; the arrows indicate the direction 



of blood flow. 



(Upper figure from W. Stempell, "Zoologie im Grundi-iss," 1926.) 



way of the anterior aorta and the posterior aorta. The complete cir- 

 culation should be understood from textbook figures and descriptions. 

 Draw ( X 3) the pericardial cavity and its contents. 



